CN111665296B - Method and device for measuring three-dimensional radiation sound field of ultrasonic transducer based on EMAT - Google Patents
Method and device for measuring three-dimensional radiation sound field of ultrasonic transducer based on EMAT Download PDFInfo
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Abstract
The invention provides a method and a device for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on EMAT. The method comprises the following steps: selecting a plurality of test blocks with different thicknesses, and determining a thickness sequence of the test blocks; exciting an ultrasonic transducer to be tested to generate ultrasonic waves in a test block according to the thickness sequence; scanning the test block by using an electromagnetic ultrasonic transducer according to preset scanning parameters so as to receive ultrasonic waves; according to the received ultrasonic waves, determining the two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested, which corresponds to test blocks with different thicknesses; and determining the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested according to the two-dimensional radiation sound field distribution. The invention solves the defects of the traditional water immersion method and photoelastic method in measuring the radiation sound field of the ultrasonic transducer, particularly in measuring the radiation sound field of the EMAT, and can accurately know the distribution characteristics of the three-dimensional radiation sound field of the ultrasonic transducer in the actual test block of the detected material by scanning and measuring the test blocks with different thicknesses.
Description
Technical Field
The invention relates to the field of ultrasonic nondestructive detection, in particular to a technology for measuring a three-dimensional radiation sound field of an ultrasonic transducer, and particularly relates to a method and a device for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on EMAT.
Background
In ultrasonic nondestructive testing, how to quickly and accurately acquire the position and the size of a defect and ensure the accuracy and the reliability of a detection result is always an important research content in the nondestructive testing. The traditional ultrasonic detection method utilizes a piezoelectric ultrasonic transducer, namely utilizes the piezoelectric effect of a piezoelectric crystal to excite ultrasonic waves, and the mode has the advantages of strong excitation signals, high detection sensitivity and the like. However, ultrasonic waves in the piezoelectric ultrasonic detection method are excited in a piezoelectric crystal, and the propagation of the ultrasonic waves in the air causes serious energy loss. Therefore, in order to reduce the loss of ultrasonic energy in the air, the piezoelectric ultrasonic detection method needs to smear a couplant between the piezoelectric crystal and the block to be tested to ensure acoustic impedance matching, so that the ultrasonic energy can be smoothly transmitted from the piezoelectric crystal to the block to be tested.
From the above analysis, it can be seen that the ultrasonic transducer is a key component for implementing ultrasonic excitation and reception, and is an important component in the whole ultrasonic detection system, namely, the performance of the piezoelectric ultrasonic transducer or the electromagnetic ultrasonic transducer is one of keys affecting the accuracy and reliability of ultrasonic nondestructive detection. Further, it is desirable for ultrasonic transducer designers to design transducers of different radiated sound fields to meet different field detection requirements; for the user of the ultrasonic transducer, the radiation sound field of the ultrasonic transducer is an important basis for making the detection process in actual detection. Therefore, in both the design and the use process of the ultrasonic transducer, in order to ensure the detection accuracy and reliability, the distribution characteristics of the radiation sound field of the ultrasonic wave excited by the ultrasonic transducer need to be accurately known, that is, the radiation sound field of the ultrasonic transducer needs to be actually measured. There are two traditional methods for measuring the sound field of an ultrasonic transducer: a water immersion method; and secondly, photoelastic method.
The water immersion method is to immerse the piezoelectric transducer to be measured in water, and use the hydrophone as the receiving ultrasonic transducer to receive the ultrasonic signal from the transducer to be measured. The distance between the inclination angle of the piezoelectric ultrasonic transducer and the hydrophone is changed, the sound field of the transducer is measured step by measuring ultrasonic signal amplitude values when different distances and different inclination angles, and as longitudinal waves can only be transmitted in water and transverse waves can not be transmitted, the water immersion method can only measure the piezoelectric longitudinal wave transducer. However, for electromagnetic ultrasonic transducers, the detection block is an important component, and ultrasonic waves can only be excited and transmitted in the metal block, so that the water immersion method is not suitable for measuring the radiation sound field of the EMAT. In addition, the sound velocity and the sound impedance of water are greatly different from those of the actually detected metal materials, the sound field measured by the water immersion method is greatly different from the sound field transmitted by the transducer in the detected test block in the actual detection, and particularly for the EMAT, the measurement result of the method cannot accurately reflect the radiation sound field characteristic of the transducer in the detected object.
The photoelastic method is based on a dynamic photoelastic method, wherein a piezoelectric ultrasonic transducer is arranged on a transparent solid sample, and a coupling agent is smeared between the piezoelectric ultrasonic transducer and the sample. The piezoelectric ultrasonic transducer is excited to generate ultrasonic waves, and the radiation sound field is shot and imaged by the digital CCD camera. The photoelastic method can be used for measuring the piezoelectric ultrasonic transverse wave transducer and the longitudinal wave transducer. However, for electromagnetic ultrasonic transducers, the excitation and propagation of ultrasonic waves are all in metal materials, and photoelastic method is usually used as an ultrasonic propagation medium by transparent organic glass, so photoelastic method is not suitable for measuring the radiation sound field generated by the excitation of the EMAT. And the photoelastic method has low sensitivity, the system is greatly influenced by noise, and the experimental measurement system is more complicated.
Disclosure of Invention
In order to solve the problems of the traditional ultrasonic transducer sound field measurement method, the embodiment of the invention provides a method for measuring the ultrasonic transducer three-dimensional radiation sound field based on EMAT, which comprises the following steps:
selecting a plurality of test blocks with different thicknesses, and determining a thickness sequence of the test blocks;
exciting an ultrasonic transducer to be tested to generate ultrasonic waves in the test block according to the thickness sequence;
scanning the test block by using an electromagnetic ultrasonic transducer according to preset scanning parameters so as to receive the ultrasonic waves;
According to the received ultrasonic waves, determining two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested, which corresponds to test blocks with different thicknesses;
And determining the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested according to the two-dimensional radiation sound field distribution.
Optionally, in an embodiment of the present invention, the scanning the test block with the electromagnetic ultrasonic transducer according to a preset scanning parameter, so as to receive the ultrasonic wave includes: and in a preset scanning area on the section of the test block, scanning the test block by using an electromagnetic ultrasonic transducer according to a preset scanning step distance and a preset scanning path so as to receive the ultrasonic waves.
Optionally, in an embodiment of the present invention, the determining, according to the two-dimensional radiation sound field distribution characteristic, a three-dimensional radiation sound field distribution of the measured ultrasonic transducer includes: and calculating the sound field values of the three-dimensional space points of the sound field region by adopting an interpolation algorithm according to the two-dimensional radiation sound field distribution values corresponding to the test blocks with different thicknesses, so as to obtain the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested.
Optionally, in an embodiment of the present invention, the method further includes: and determining the relation between the sound beam and sound pressure of the ultrasonic transducer to be tested and the propagation distance according to the two-dimensional radiation sound field distribution.
Optionally, in an embodiment of the present invention, the method further includes: acquiring a self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and a self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer; determining an influence coefficient according to the self-excitation self-receiving signal of the ultrasonic transducer to be measured under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be measured which is not under the influence of the electromagnetic ultrasonic transducer; and compensating the relation between the three-dimensional radiation sound field distribution, the sound beam, the sound pressure and the propagation distance according to the influence coefficient.
The embodiment of the invention also provides a device for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on the EMAT, which comprises:
The test block selecting module is used for selecting a plurality of test blocks with different thicknesses and determining the thickness sequence of the test blocks;
the ultrasonic excitation module is used for exciting the ultrasonic transducer to be tested to generate ultrasonic waves in the test block according to the thickness sequence;
The ultrasonic scanning module is used for scanning the test block by using an electromagnetic ultrasonic transducer according to preset scanning parameters so as to receive the ultrasonic waves;
The two-dimensional sound field distribution module is used for determining the two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested, which corresponds to test blocks with different thicknesses, according to the received ultrasonic waves;
and the three-dimensional sound field distribution module is used for determining the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested according to the two-dimensional radiation sound field distribution.
Optionally, in an embodiment of the present invention, the ultrasonic scanning module includes: and the ultrasonic scanning unit is used for scanning the test block by using an electromagnetic ultrasonic transducer according to a preset scanning step distance and a preset scanning path in a preset scanning area on the section of the test block so as to receive the ultrasonic waves.
Optionally, in an embodiment of the present invention, the three-dimensional sound field distribution module includes: and the three-dimensional sound field distribution unit is used for calculating the sound field values of the three-dimensional space points of the sound field region by adopting an interpolation algorithm according to the two-dimensional radiation sound field distribution values corresponding to the test blocks with different thicknesses, so as to obtain the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested.
Optionally, in an embodiment of the present invention, the apparatus further includes: and the sound beam and sound pressure module is used for determining the relation between the sound beam and sound pressure of the ultrasonic transducer to be tested and the propagation distance according to the two-dimensional radiation sound field distribution.
Optionally, in an embodiment of the present invention, the apparatus further includes: the self-excitation self-receiving signal module is used for acquiring the self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer; the influence coefficient module is used for determining an influence coefficient according to the self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer; and the compensation module is used for compensating the relation between the three-dimensional radiation sound field distribution, the sound beam, the sound pressure and the propagation distance according to the influence coefficient.
The invention solves a plurality of defects existing in the traditional water immersion method and photoelastic method when measuring the radiation sound field of the ultrasonic transducer, in particular to the aspect of measuring the radiation sound field of the EMAT based on EMAT tomography. The distribution characteristics of the ultrasonic transducer three-dimensional radiation sound field in the actual test block of the detected material can be accurately known by scanning and measuring test blocks with different thicknesses.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the description below are only some embodiments of the invention and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on EMAT according to an embodiment of the invention;
FIG. 2 is a schematic diagram of radiation acoustic field tomography in an embodiment of the present invention;
FIG. 3 is a flow chart of a tomographic scan of a radiation sound field in an embodiment of the invention;
FIG. 4 is a graph showing compensation coefficients of a received signal according to an embodiment of the present invention;
FIGS. 5A-5G are graphs showing two-dimensional radiation sound field distribution at different thicknesses according to an embodiment of the present invention;
FIG. 6 is a three-dimensional distribution of radiated sound fields in an embodiment of the present invention;
FIG. 7 is a view showing the width of a sound beam of a radiation sound field according to an embodiment of the present invention;
FIG. 8 is a graph of sound pressure on the axis of a radiated sound field in an embodiment of the present invention;
Fig. 9 is a schematic structural diagram of an apparatus for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on an EMAT according to an embodiment of the present invention.
Detailed Description
The embodiment of the invention provides a method and a device for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on EMAT.
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The core of the electromagnetic ultrasonic detection technology is an electromagnetic ultrasonic transducer, and the transducer mainly comprises three parts: a magnet, a coil, a detected conductor or a magnetic conductive material. The working principle of the electromagnetic ultrasonic transducer is as follows: the magnet generates a bias magnetic field, high-frequency alternating current is introduced into the coil, eddy current is induced on the surface of the detected material, and ultrasonic waves are excited on the surface of the detected material under the action of the bias magnetic field. The electromagnetic ultrasonic transducer (EMAT) is utilized to realize ultrasonic nondestructive detection, and has the advantages of high precision, no need of couplant, non-contact, suitability for high-temperature detection, easy excitation of various ultrasonic waveforms and the like. Wherein, it is notable that the detected conductor or the magnetic conductive material is an integral part of EMAT for realizing transduction. In the traditional water immersion method in the ultrasonic transducer sound field measuring method, only the piezoelectric longitudinal wave transducer can be measured by the water immersion method because only longitudinal waves can be transmitted in water and transverse waves cannot be transmitted. However, for electromagnetic ultrasonic transducers, the detection block is an important component, and ultrasonic waves can only be excited and transmitted in the metal block, so that the water immersion method is not suitable for measuring the radiation sound field of the EMAT. Moreover, the sound velocity and the sound impedance of water are greatly different from those of the actually detected metal materials, the sound field measured by the water immersion method is greatly different from the sound field transmitted by the transducer in the detected test block in the actual detection, and particularly for the EMAT, the measurement result of the method cannot accurately reflect the radiation sound field characteristics of the transducer in the detected object. The photoelastic method in the traditional ultrasonic transducer sound field measuring method can be used for measuring the piezoelectric ultrasonic transverse wave transducer and the longitudinal wave transducer. However, for electromagnetic ultrasonic transducers, the transduction principle is different from that of piezoelectric ultrasonic transducers, the excitation and the propagation of ultrasonic waves are in a detected metal detection test block, and the sound field characteristics of the electromagnetic ultrasonic transducers are closely related to the material characteristics of detected metals. On the one hand, the electromagnetic ultrasonic transducer cannot be directly excited in the organic glass to generate ultrasonic waves; on the other hand, the radiation sound field measured in the organic glass cannot truly reflect the radiation sound field characteristics of the electromagnetic ultrasonic transducer in a certain metal material. Photoelastic method is therefore not suitable for measuring the radiation sound field generated by excitation of electromagnetic ultrasonic transducers. And the photoelastic method has low sensitivity, the system is greatly influenced by noise, and the experimental measurement system is more complicated.
According to the invention, the ultrasonic radiation sound field excited by the ultrasonic transducer in the metal test block is scanned and measured by the three-dimensional radiation sound field tomography method. Fig. 1 is a flowchart of a method for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on an EMAT according to an embodiment of the present invention, where the method includes: step S1, selecting a plurality of test blocks with different thicknesses, and determining a thickness sequence of the test blocks; specifically, the test blocks with different thicknesses are arranged according to a preset rule, for example, according to the thickness values from large to small, so as to obtain a thickness sequence of the test blocks.
S2, exciting an ultrasonic transducer to be tested to generate ultrasonic waves in the test block according to the thickness sequence; wherein the test block is made of conductive or magnetic conductive material.
Step S3, scanning the test block by using an electromagnetic ultrasonic transducer according to preset scanning parameters so as to receive the ultrasonic waves; the ultrasonic transducer to be tested is a transducer capable of exciting stress waves such as ultrasonic waves, surface waves, ultrasonic guided waves and the like. Specifically, the ultrasonic transducer to be tested and the electromagnetic ultrasonic transducer are respectively arranged on two opposite surfaces in the thickness direction of the test block, and after the ultrasonic transducer to be tested sends out ultrasonic waves, the electromagnetic ultrasonic transducer scans the test block according to preset scanning parameters and receives the ultrasonic waves. After the scanning is completed, another test block is replaced, ultrasonic waves are generated by the ultrasonic transducer to be tested, and the ultrasonic waves are received by the electromagnetic ultrasonic transducer until the scanning of all the test blocks with different thicknesses is completed.
S4, determining two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested, which corresponds to test blocks with different thicknesses, according to the received ultrasonic waves; and obtaining the two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested according to the received ultrasonic waves.
And S5, determining the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested according to the two-dimensional radiation sound field distribution. Specifically, the two-dimensional radiation sound field distribution may be superimposed, thereby obtaining a three-dimensional radiation sound field distribution of the ultrasonic transducer to be measured.
As an embodiment of the present invention, the scanning the test block with the electromagnetic ultrasonic transducer according to the preset scanning parameters includes: and in a preset scanning area on the section of the test block, scanning the test block by using an electromagnetic ultrasonic transducer according to a preset scanning step distance and a preset scanning path so as to receive the ultrasonic waves.
As one embodiment of the present invention, the determining the three-dimensional radiation sound field distribution of the ultrasonic transducer under test according to the two-dimensional radiation sound field distribution characteristics includes: and calculating the sound field values of the three-dimensional space points of the sound field region by adopting an interpolation algorithm according to the two-dimensional radiation sound field distribution values corresponding to the test blocks with different thicknesses, so as to obtain the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested.
According to the two-dimensional radiation sound field distribution, the relation between the sound beam and sound pressure of the ultrasonic transducer to be measured and the propagation distance is determined. Specifically, the relation between the sound beam and the propagation distance can be expressed as a sound beam distribution curve, wherein the diameter range of the sound pressure amplitude attenuated by-6 db from the maximum value in the two-dimensional distribution diagram of the radiation sound field under each thickness is extracted, and the distribution curve of the sound beam along with the propagation distance is obtained. In addition, the relationship between the sound pressure and the propagation distance can be expressed as a sound pressure distribution curve, wherein the maximum value of the sound pressure in the two-dimensional distribution diagram of the radiation sound field under each thickness is extracted, namely, the distribution curve of the sound pressure of the radiation sound field along with the propagation distance is drawn.
In this embodiment, a self-excited self-received signal of the ultrasonic transducer under the influence of the electromagnetic ultrasonic transducer and a self-excited self-received signal of the ultrasonic transducer under the influence of the electromagnetic ultrasonic transducer are obtained; determining an influence coefficient according to the self-excitation self-receiving signal of the ultrasonic transducer to be measured under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be measured which is not under the influence of the electromagnetic ultrasonic transducer; and compensating the relation between the three-dimensional radiation sound field distribution, the sound beam, the sound pressure and the propagation distance according to the influence coefficient.
Specifically, when the material of the measurement test block is a nonferromagnetic material, the influence of the electromagnetic ultrasonic transducer on the radiation sound field of the ultrasonic transducer to be measured needs to be considered, and the measurement result is compensated. Specifically, the self-excitation self-receiving signals of the ultrasonic transducer to be measured when the electromagnetic ultrasonic transducer is positioned at different positions, namely the self-excitation self-receiving signals of the ultrasonic transducer to be measured under the influence of the electromagnetic ultrasonic transducer, and the self-excitation self-receiving signals of the ultrasonic transducer to be measured when the magnetic field of the electromagnetic ultrasonic transducer is not influenced, namely the self-excitation self-receiving signals of the ultrasonic transducer to be measured under the influence of the electromagnetic ultrasonic transducer, are respectively acquired. By comparing and analyzing the signals acquired under the two conditions, the influence coefficient of the electromagnetic ultrasonic transducer on the radiation sound field of the ultrasonic transducer to be measured can be obtained when the electromagnetic ultrasonic transducer is positioned at different positions, and further the compensation coefficient for eliminating the influence of the electromagnetic ultrasonic transducer on the radiation sound field of the ultrasonic transducer to be measured is obtained.
The invention provides a measuring method of three-dimensional radiation sound field tomography, which comprises the following steps: namely, the metal test block is divided into test blocks with different thicknesses in the thickness direction, the thicknesses of the test blocks in the near field region of the radiation sound field are respectively L1, L2, L3, L4 and L5 … …, and the thicknesses of the test blocks in the far field region are respectively Y1, Y2, Y3, Y4 and Y5 … …. The ultrasonic excitation receiving mode adopts a transmitting-receiving mode, namely ultrasonic signals of the ultrasonic transducer to be detected on test blocks with different thicknesses are scanned and received through the receiving ultrasonic transducer, a two-dimensional distribution diagram of the radiation sound field of the ultrasonic transducer to be detected in different depth directions is obtained, the two-dimensional distribution diagram of the radiation sound field with different thicknesses is overlapped, and the change of the radiation sound field in the thickness direction is drawn. And drawing a change curve of sound beams and sound pressure along with the propagation distance in the radiation sound field by extracting image information of each radiation sound field.
In a specific embodiment of the present invention, the tomographic method divides the metal test block into test blocks with different thicknesses in the thickness direction, and the thicknesses of the test blocks in the near field region of the radiation sound field are L1, L2, L3, L4, L5 … …, and the thicknesses of the test blocks in the far field region are Y1, Y2, Y3, Y4, Y5 … …. The ultrasonic excitation receiving mode adopts a transmitting-receiving mode, namely ultrasonic signals of the ultrasonic transducer to be detected on test blocks with different thicknesses are scanned and received through the receiving ultrasonic transducer, a two-dimensional distribution diagram of the radiation sound field of the ultrasonic transducer to be detected in different depth directions is obtained, the two-dimensional distribution diagram of the radiation sound field with different thicknesses is overlapped, and the change of the radiation sound field in the thickness direction is drawn. And drawing a change curve of sound beams and sound pressure along with the propagation distance in the radiation sound field by extracting image information of each radiation sound field.
Fig. 2 is a schematic diagram of measuring an ultrasonic transducer radiation sound field based on EMAT tomography, which specifically includes: one part is excitation and reception of ultrasonic signals, and a Pitch-Catch (Pitch-Catch) mode is adopted during measurement, namely, an ultrasonic transducer 22 to be measured and an electromagnetic ultrasonic transducer (receiving EMAT) 23 are respectively arranged on two opposite surfaces along the thickness direction of the test block 21, for example, the ultrasonic transducer to be measured is contacted with the lower surface of the test block, and the receiving EMAT is arranged on the upper surface of the test block. During measurement, an excitation signal is output by the signal generator, amplified by the power amplifier and then input into the ultrasonic transducer to be measured, ultrasonic waves are generated by excitation and propagated in the tested test block, and an electromagnetic ultrasonic transducer (EMAT) positioned on the other surface of the test block is used for receiving the ultrasonic waves on the surface of the test block, and the received signal is collected by the signal collector after being amplified by the signal amplifier and stored by the computer and is subjected to post-processing. The other part is mechanical scanning, and the carrying and receiving EMAT performs scanning movement in a scanning area 25 on the surface of the test block by utilizing a three-coordinate mechanical sliding table 24 or a mechanical arm, so as to realize the two-dimensional radiation sound field distribution measurement on the surface of the test block.
The tomographic flow chart is shown in fig. 3, and specifically includes the following steps:
(1) An ultrasound-detectable material object is determined. The propagation medium of the ultrasonic wave when the ultrasonic transducer radiates the sound field is determined, namely the test block material adopted in measurement is determined.
(2) A radiation sound field measurement range is determined. Determining the depth of a radiation sound field to be tested, and setting a test block thickness sequence of tomography;
(3) And installing the ultrasonic transducer to be tested, a test block and receiving EMAT. According to the test schematic diagram 2, the arrangement mode of the tested sensor and the receiving EMAT is one-to-one, and the tested ultrasonic transducer, the test block and the receiving EMAT are installed according to the mode.
(4) And (5) scanning setting. According to the radiation sound field measurement requirement, determining the measurement range on each section, namely setting the scanning area and the scanning step distance of each layer of thick test block, and planning a scanning path;
(5) Two-dimensional radiation sound field scanning. And exciting the ultrasonic transducer to be tested to generate ultrasonic waves in the test block, and controlling the receiving EMAT to scan the radiation sound field of the ultrasonic transducer to be tested on the surface of the test block according to the set scanning path.
(6) And (5) replacing the test block, and repeating the step (5). And replacing test blocks with different thicknesses, and performing two-dimensional radiation sound scanning on the test blocks with different thicknesses until the scanning of all series of test blocks with different thicknesses is completed.
(7) And (5) data post-processing. And carrying out post-processing on the signals obtained by the received EMAT scanning to obtain the two-dimensional radiation sound field distribution characteristics of the ultrasonic transducer to be tested in each thickness, so as to obtain the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested in the whole thickness direction. In the signal post-processing process, the influence of the received EMAT on the measurement result needs to be considered, namely, the magnetic field generated by the permanent magnet in the received EMAT can influence the transduction process of the ultrasonic transducer to be measured, and the influence caused by the received EMAT is eliminated mainly aiming at the condition that the ultrasonic transducer to be measured is the EMAT.
In a specific embodiment of the present invention, the measured ultrasonic transducer is a toroidal coil EMAT as an implementation case, and radiation sound field measurement is performed on the measured ultrasonic transducer, so that the present invention will be described in further detail. The EMAT tomographic measurement-based method shown in FIG. 3 specifically comprises two parts: and one part of the ultrasonic signal receiving system consists of a signal ultrasonic excitation system formed by tested annular coil EMAT, a signal generator, a power amplifier and test blocks with different thicknesses, a receiving EMAT, a signal amplifier, a signal collector, a computer and the like. The other part is mechanical scanning, which consists of an optical horizontal table and a three-coordinate mechanical horizontal sliding table, wherein the stroke range of the axis of the three-coordinate mechanical horizontal sliding table X, Y, Z is 500 multiplied by 500mm.
(1) The material object for ultrasonic detection is Aluminum (AL) which is a metal material.
(2) The toroidal coil EMAT is measured. The measuring depth of the radiation sound field is 40mm, and the set tomographic thickness test block sequences are 4mm, 6mm, 8mm, 10mm, 20mm, 30mm and 40mm.
(3) The receiving EMAT is arranged on the Z axis of a three-coordinate mechanical horizontal sliding table, and the annular coil EMAT is arranged and fixed on an optical level through a clamp. The center of the receive EMAT is aligned with the center of the ring-shaped EMAT by adjustment. The test block is arranged between the two transducers, the lower surface of the test block is contacted with the tested annular coil EMAT, and the upper surface of the test block is contacted with the receiving EMAT. The intersection point of the transducer center and the upper surface of the test block serves as the origin of the scan coordinates.
(4) Taking the diffusivity of the radiation sound field of the transducer into consideration, selecting a test block (40 mm thick) at the maximum depth for B scanning, and determining an acquisition area. B scanning is carried out on the scanning coordinates along the X-axis direction, the step distance is 1mm, and the distribution of the annular coil EMAT radiation sound field on the central line is obtained through analysis. And finally determining that the scanning area of each layer of thick test block is 27mm multiplied by 27mm, wherein a serpentine scanning is adopted for a scanning path, and the scanning step distance is 1mm, namely, the scanning step distance is 1mm in two directions of X, Y.
(5) Radiation acoustic field tomography. The control signal generator generates a 3-period Hanning window modulated sine wave with the center frequency of 3.5MHz as an excitation signal, and the sine wave is amplified by the power square amplifier and then input into the annular coil EMAT to excite the annular coil EMAT to generate ultrasonic waves in the test block. The receiving EMAT is controlled to realize point-by-point scanning in the scanning area, ultrasonic signal receiving of the upper surface of the test block is completed at each scanning point, the ultrasonic signal is amplified by the signal amplifier, collected by the signal collector and transmitted to the computer for storage.
(6) And (5) replacing test blocks with different thicknesses, and repeating the step (5) until all the thickness test blocks are scanned.
(7) And (5) data post-processing. The permanent magnets in the EMAT provide a static bias magnetic field, and the magnitude of the static magnetic field can influence the radiation sound field of the EMAT. The test block is made of aluminum material and is made of nonferromagnetic material, a magnetic field generated by a permanent magnet in the EMAT is received and can be overlapped with the magnetic field in the annular coil EMAT, so that the radiation sound field of the annular coil EMAT is influenced, and in the process of receiving the scanning movement of the EMAT, the influence coefficients of the annular coil EMAT at different positions are different. And for test blocks with different thicknesses, the influence coefficients are also different, so that when the test blocks with different thicknesses are measured, the measurement results are required to be correspondingly compensated.
Compensation curve measurement: and scanning the sound field along the X-axis direction in a B scanning mode in a scanning coordinate, wherein the step is 1mm, collecting self-excitation self-receiving signals of the annular coil EMAT when the received ultrasonic EMAT is positioned at different positions, taking the echo amplitude value as A x, collecting the self-excitation self-receiving signals of the annular coil EMAT when the magnetic field of the EMAT is not influenced, and taking the echo amplitude value as A 0. Dividing the echo amplitude A x of the received EMAT magnetic field at different positions by the echo amplitude A 0 of the received EMAT magnetic field at no magnetic field to obtain the influence coefficient of the received EMAT magnetic field at different positions on the excitation signal. And further, a compensation coefficient curve for eliminating the influence of the received EMAT on the radiation sound field of the EMAT to be tested can be obtained, as shown in fig. 4. The principle of correcting the measurement result by using the compensation coefficient is as follows:
Where A i is the result of the compensation correction and y i is the measured value of the acoustic field of the sensor under test that receives the EMAT scan.
(8) As shown in fig. 5A to 5G, in order to compensate the original received data by using a compensation curve, the echo amplitude after correction and compensation is obtained, and the two-dimensional radiation sound field distribution diagram of fig. 5A to 5G under different thicknesses is obtained. Wherein, FIG. 5A is a two-dimensional radiation sound field distribution diagram under an AL block with a thickness of 4mm, FIG. 5B is a two-dimensional radiation sound field distribution diagram under an AL block with a thickness of 6mm, FIG. 5C is a two-dimensional radiation sound field distribution diagram under an AL block with a thickness of 8mm, FIG. 5D is a two-dimensional radiation sound field distribution diagram under an AL block with a thickness of 10mm, FIG. 5E is a two-dimensional radiation sound field distribution diagram under an AL block with a thickness of 20mm, FIG. 5F is a two-dimensional radiation sound field distribution diagram under an AL block with a thickness of 30mm, and FIG. 5G is a two-dimensional radiation sound field distribution diagram under an AL block with a thickness of 40 mm.
(9) As shown in fig. 6, the three-dimensional radiation sound field can be obtained by performing interpolation calculation on the radiation sound field obtained by measurement by using a three-dimensional interpolation algorithm.
(10) As shown in fig. 7, the beam width of the three-dimensional radiation acoustic field excited by the toroidal coil EMAT in the thickness direction varies with the propagation distance.
(11) As shown in fig. 8, the signal amplitude of the center point of the scanning area in each thickness AL block is extracted to draw an on-axis sound pressure graph of the radiation sound field excited by the annular coil in the AL block.
The invention solves a plurality of defects existing in the traditional water immersion method and photoelastic method when measuring the radiation sound field of the ultrasonic transducer, in particular to the aspect of measuring the radiation sound field of the EMAT based on EMAT tomography. The distribution characteristics of the ultrasonic transducer three-dimensional radiation sound field in the actual test block of the detected material can be accurately known by scanning and measuring test blocks with different thicknesses, and the change of sound beams and sound pressure along with the propagation distance in the radiation sound field can be determined by extracting the information on the test blocks with different thicknesses.
Fig. 9 is a schematic structural diagram of an apparatus for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on an EMAT according to an embodiment of the present invention, where the apparatus includes: the test block selecting module 10 is used for selecting a plurality of test blocks with different thicknesses and determining the thickness sequence of the test blocks;
the ultrasonic excitation module 20 is used for exciting the ultrasonic transducer to be tested to generate ultrasonic waves in the test block according to the thickness sequence;
The ultrasonic scanning module 30 is configured to scan the test block with an electromagnetic ultrasonic transducer according to preset scanning parameters, so as to receive the ultrasonic wave;
The two-dimensional sound field distribution module 40 is used for determining two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested, which corresponds to test blocks with different thicknesses, according to the received ultrasonic waves;
the three-dimensional radiation sound field distribution module 50 is configured to determine a three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested according to the two-dimensional radiation sound field distribution.
As one embodiment of the present invention, the ultrasonic scanning module includes: and the ultrasonic scanning unit is used for scanning the test block by using an electromagnetic ultrasonic transducer according to a preset scanning step distance and a preset scanning path in a preset scanning area on the section of the test block so as to receive the ultrasonic waves.
As one embodiment of the present invention, the three-dimensional sound field distribution module includes: and the three-dimensional sound field distribution unit is used for superposing the two-dimensional radiation sound field distribution corresponding to the test blocks with different thicknesses to obtain the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested.
As an embodiment of the present invention, the apparatus further comprises: and the sound beam and sound pressure module is used for determining the relation between the sound beam and sound pressure of the ultrasonic transducer to be tested and the propagation distance according to the two-dimensional radiation sound field distribution.
In this embodiment, the apparatus further includes: the self-excitation self-receiving signal module is used for acquiring the self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer; the influence coefficient module is used for determining an influence coefficient according to the self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer; and the compensation module is used for compensating the relation between the three-dimensional radiation sound field distribution, the sound beam, the sound pressure and the propagation distance according to the influence coefficient.
Based on the same application conception as the method for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on the EMAT, the invention also provides a device for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on the EMAT. Because the principle of solving the problem of the device for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on the EMAT is similar to that of the device for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on the EMAT, the implementation of the device for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on the EMAT can be referred to the implementation of the method for measuring the three-dimensional radiation sound field of the ultrasonic transducer based on the EMAT, and repeated parts are omitted.
The invention solves a plurality of defects existing in the traditional water immersion method and photoelastic method when measuring the radiation sound field of the ultrasonic transducer, in particular to the aspect of measuring the radiation sound field of the EMAT based on EMAT tomography. The distribution characteristics of the ultrasonic transducer three-dimensional radiation sound field in the actual test block of the detected material can be accurately known by scanning and measuring test blocks with different thicknesses, and the change of sound beams and sound pressure along with the propagation distance in the radiation sound field can be determined by extracting the information on the test blocks with different thicknesses.
Those of ordinary skill in the art will appreciate that all or a portion of the steps in implementing the methods of the above embodiments may be implemented by a program that instructs associated hardware, and the program may be stored on a computer readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (6)
1. A method for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on an EMAT, the method comprising:
selecting a plurality of test blocks with different thicknesses, and determining a thickness sequence of the test blocks;
exciting an ultrasonic transducer to be tested to generate ultrasonic waves in the test block according to the thickness sequence;
scanning the test block by using an electromagnetic ultrasonic transducer according to preset scanning parameters so as to receive the ultrasonic waves;
According to the received ultrasonic waves, determining two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested, which corresponds to test blocks with different thicknesses;
According to the two-dimensional radiation sound field distribution, determining the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested;
wherein the method further comprises: according to the two-dimensional radiation sound field distribution, determining the relation between the sound beam and sound pressure of the ultrasonic transducer to be tested and the propagation distance;
wherein the method further comprises:
Acquiring a self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and a self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer;
determining an influence coefficient according to the self-excitation self-receiving signal of the ultrasonic transducer to be measured under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be measured which is not under the influence of the electromagnetic ultrasonic transducer;
Compensating the relation between the three-dimensional radiation sound field distribution, sound beams, sound pressure and propagation distance according to the influence coefficient;
wherein the method further comprises:
A data post-processing process comprising: the permanent magnet in the EMAT provides a static bias magnetic field, the size of the static bias magnetic field affects the radiation sound field of the EMAT, the test block is made of nonferromagnetic materials, the static bias magnetic field generated by the permanent magnet in the EMAT is received and overlapped with the magnetic field in the annular coil EMAT to affect the radiation sound field of the annular coil EMAT, and in the process of receiving the scanning movement of the EMAT, the influence coefficients of the magnetic field at different positions are different; for test blocks with different thicknesses, the influence coefficients are different, and when the test blocks with different thicknesses are measured, corresponding compensation is carried out on the measurement results;
A compensation curve measurement process comprising: scanning a sound field along the X-axis direction in a B scanning mode in a scanning coordinate, wherein the step is 1mm, collecting self-excitation self-receiving signals of the annular coil EMAT when the received ultrasonic EMAT is positioned at different positions, taking the echo amplitude value as A x, collecting self-excitation self-receiving signals of the annular coil EMAT when the magnetic field of the EMAT is not received, and taking the echo amplitude value as A 0; dividing the echo amplitude A x of the received EMAT magnetic field at different positions by the echo amplitude A 0 of the received EMAT magnetic field without the magnetic field to obtain the influence coefficients of the received EMAT magnetic field on the excitation signals at different positions so as to obtain a compensation coefficient curve for eliminating the influence of the received EMAT on the radiation sound field of the tested EMAT, and correcting the measurement result by using the compensation coefficient:
Wherein A i is the result after compensation and correction, and y i is the measured value of the sound field of the sensor to be tested after receiving EMAT scanning.
2. The method of claim 1, wherein scanning the test block with an electromagnetic ultrasonic transducer to receive the ultrasonic waves according to preset scanning parameters comprises: and in a preset scanning area on the section of the test block, scanning the test block by using an electromagnetic ultrasonic transducer according to a preset scanning step distance and a preset scanning path so as to receive the ultrasonic waves.
3. The method of claim 1, wherein determining the three-dimensional radiation sound field distribution of the ultrasonic transducer under test from the two-dimensional radiation sound field distribution characteristics comprises: and calculating the sound field values of the three-dimensional space points of the sound field region by adopting an interpolation algorithm according to the two-dimensional radiation sound field distribution values corresponding to the test blocks with different thicknesses, so as to obtain the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested.
4. An apparatus for measuring a three-dimensional radiation sound field of an ultrasonic transducer based on an EMAT, the apparatus comprising:
The test block selecting module is used for selecting a plurality of test blocks with different thicknesses and determining the thickness sequence of the test blocks;
the ultrasonic excitation module is used for exciting the ultrasonic transducer to be tested to generate ultrasonic waves in the test block according to the thickness sequence;
The ultrasonic scanning module is used for scanning the test block by using an electromagnetic ultrasonic transducer according to preset scanning parameters so as to receive the ultrasonic waves;
The two-dimensional sound field distribution module is used for determining the two-dimensional radiation sound field distribution of the ultrasonic transducer to be tested, which corresponds to test blocks with different thicknesses, according to the received ultrasonic waves;
The three-dimensional sound field distribution module is used for determining the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested according to the two-dimensional radiation sound field distribution;
Wherein the apparatus further comprises: the sound beam and sound pressure module is used for determining the relation between the sound beam and sound pressure of the ultrasonic transducer to be tested and the propagation distance according to the two-dimensional radiation sound field distribution;
Wherein the apparatus further comprises:
the self-excitation self-receiving signal module is used for acquiring the self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer;
the influence coefficient module is used for determining an influence coefficient according to the self-excitation self-receiving signal of the ultrasonic transducer to be tested under the influence of the electromagnetic ultrasonic transducer and the self-excitation self-receiving signal of the ultrasonic transducer to be tested which is not under the influence of the electromagnetic ultrasonic transducer;
The compensation module is used for compensating the relation between the three-dimensional radiation sound field distribution, the sound beam, the sound pressure and the propagation distance according to the influence coefficient;
The influence coefficient module is also used for providing a static bias magnetic field for the permanent magnet in the EMAT, the size of the static bias magnetic field influences the radiation sound field of the EMAT, the test block is made of nonferromagnetic materials, receives the static bias magnetic field generated by the permanent magnet in the EMAT, is overlapped with the magnetic field in the annular coil EMAT to influence the radiation sound field of the annular coil EMAT, and in the process of receiving the scanning movement of the EMAT, the influence coefficients of the permanent magnet in different positions are different; for test blocks with different thicknesses, the influence coefficients are different, and when the test blocks with different thicknesses are measured, corresponding compensation is carried out on the measurement results;
The compensation module is also used for scanning the sound field along the X-axis direction in a B scanning mode in a scanning coordinate, wherein the step is 1mm, collecting self-excitation self-receiving signals of the annular coil EMAT when the received ultrasonic EMAT is positioned at different positions, taking the echo amplitude value as A x, collecting self-excitation self-receiving signals of the annular coil EMAT when the influence of the magnetic field of the EMAT is not received, and taking the echo amplitude value as A 0; dividing the echo amplitude A x of the received EMAT magnetic field at different positions by the echo amplitude A 0 of the received EMAT magnetic field without the magnetic field to obtain the influence coefficients of the received EMAT magnetic field on the excitation signals at different positions so as to obtain a compensation coefficient curve for eliminating the influence of the received EMAT on the radiation sound field of the tested EMAT, and correcting the measurement result by using the compensation coefficient:
Wherein A i is the result after compensation and correction, and y i is the measured value of the sound field of the sensor to be tested after receiving EMAT scanning.
5. The apparatus of claim 4, wherein the ultrasound scanning module comprises: and the ultrasonic scanning unit is used for scanning the test block by using an electromagnetic ultrasonic transducer according to a preset scanning step distance and a preset scanning path in a preset scanning area on the section of the test block so as to receive the ultrasonic waves.
6. The apparatus of claim 4, wherein the three-dimensional sound field distribution module comprises: and the three-dimensional sound field distribution unit is used for calculating the sound field values of the three-dimensional space points of the sound field region by adopting an interpolation algorithm according to the two-dimensional radiation sound field distribution values corresponding to the test blocks with different thicknesses, so as to obtain the three-dimensional radiation sound field distribution of the ultrasonic transducer to be tested.
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